The D coefficient increases with increasing percentage of additive
incorporation. In the a-Toc series, this increase could be
related to an arrangement in small aggregates due to the limited compatibility between the additive and the polymer. a-tocopherol phytyl chain and relatively large molecular size of the a-Toc do not bind strongly to the mainly polar polymer chains under study, but they are ‘‘physically trapped’’ in the matrix below a critical concentration.
When a greater percentage is incorporated, the size and/or
possibility of connection between these aggregates will be increased and thus the migration rate will be higher. In films loaded with BHT, no significant differences were observed by varying
the amount of additive incorporated. The high value of D
observed for a-Toc 5 wt.% films was due to the significant surface
segregation of the additive, as observed in SEM images (see Supplementary
data, Fig. S2) and for that reason this sample was excluded
from the systematic analysis.